Two key nutrients that provide insights about Lake Erie’s harmful algal blooms — dissolved reactive phosphorus and ammonium — are particularly difficult to measure. Recently, researchers made major progress developing new, low-cost sensors that can accurately measure these water quality parameters on site.
The severity and extent of harmful algal blooms in the Western Lake Erie Basin is closely linked to dissolved reactive phosphorus (DRP), and bloom toxicity is often associated with the availability of reduced forms of nitrogen, especially ammonium (NH₄). Significantly, these two nutrients are particularly difficult to measure both in the field and the laboratory because they are present at low concentrations and require special analysis. Existing technology is limited, as most sensors are unable to detect DRP and NH₄ at naturally occurring levels or are prohibitively expensive.

A team of researchers assessed water samples from various Ohio tributaries using both standard laboratory methods and new, low-cost sensors they developed to detect dissolved reactive phosphorus and ammonium.
To remedy this, a team of researchers led by Dr. Laura Johnson, who at the time served as director of the National Center for Water Quality Research at Heidelberg University, worked with a startup water sensor company to help develop and test a new technology that could analyze these important nutrients and revolutionize water quality analysis. The research was funded through the Ohio Department of Higher Education’s Harmful Algal Bloom Research Initiative (ODHE HABRI).
“The development of sensors able to detect phosphate and ammonium could revolutionize our ability to manage Lake Erie,” said Johnson, now the chief science officer at the Michigan Department of Agriculture and Rural Development. “These two nutrients are notoriously difficult to quantify but also disproportionately influence bloom dynamics in the lake.”
Using polymer technology licensed from The Ohio State University and water quality data from the National Center for Water Quality Research, the company produced ionic sensors that are selective to conditions in Ohio watersheds. Then, researchers assessed water samples from various tributaries using both standard laboratory methods and the new sensors.
The team validated that the ionically selective sensors can detect pH and low levels of NH₄, with results comparable to laboratory analysis. Development of a sensor to detect orthophosphate, a DRP equivalent, is almost complete. While the product is not yet field-deployable, the team made significant progress toward reaching that goal.
The sensors offer a number of benefits: they aren’t affected by other particles in the water, are made of relatively inexpensive materials, and can manufactured for multiple uses by being built in different shapes and sizes. Once development is completed, the sensors could be deployed on-site at crucial points at field edges, throughout rivers, and ultimately in Lake Erie. Hopefully, this technology will help decision-makers, both elected officials and agencies, address HABs in a highly robust and accurate manner.
“Low-cost sensors would not only improve our loading estimates to quantify bloom severity but could also be deployed throughout the watershed to help direct resources (e.g., funding and agricultural conservation practices) that reduce the source of these nutrients,” Johnson said. “With funding from HABRI, we were able to support development of a sensor prototype and design, though more development is needed for a market-ready sensor product.”
Ohio Sea Grant is supported by The Ohio State University College of Food, Agricultural, and Environmental Sciences (CFAES) School of Environment and Natural Resources, Ohio State University Extension, and NOAA Sea Grant, a network of 34 Sea Grant programs nation-wide dedicated to the protection and sustainable use of marine and Great Lakes resources. Stone Laboratory is Ohio State’s island campus on Lake Erie and is the research, education, and outreach facility of Ohio Sea Grant and part of CFAES School of Environment and Natural Resources.